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1.
Laine, Patrick L.
Laser flash photolysis studies of halogen atom reactions of atmospheric interest.
Degree: PhD, Earth and Atmospheric Sciences, 2011, Georgia Tech
URL: http://hdl.handle.net/1853/42817 
► The Earth's atmosphere is a large photochemical reactor consisting primarily of N2 (~78%) and O2 (~21%) with Ar and water vapor being the next most…
(more)
▼ The Earth's atmosphere is a large photochemical reactor consisting primarily of N2 (~78%) and O2 (~21%) with Ar and water vapor being the next most abundant constituents. All of the remaining gases in the atmosphere are referred to as 'trace gases', and they play a critical role in understanding climate change, urban air quality, ozone production and depletion, and in determining the overall 'health' of the atmosphere. These trace components are present in our atmosphere with mixing ratios, i.e., mole fractions, ranging from sub parts per trillion to several hundred parts per million. One class of trace constituents that play a critical role in atmospheric chemistry are free radicals. Free radicals are highly reactive, often initiating the oxidation of natural and anthropogenic atmospheric species, thereby often controlling the fate and lifetimes of these species. The research comprising this dissertation focuses on laboratory studies of the kinetics and mechanisms of free radical (atomic halogen) reactions that can impact the levels of important trace atmospheric species. In the studies reported herein, laser flash photolysis (LFP) was coupled with time resolved atomic resonance fluorescence (RF) spectroscopic detection of Cl or Br atoms to investigate halogen atom chemistry. The research addresses three groups of reactions: Cl atom reactions with alkyl bromides, Cl and Br-initiated oxidations of small (C2-C6) alkenes, and Cl reactions with CH3SCH3 (DMS, dimethylsulfide) and CH3SeCH3 (DMSe, dimethylselenide).
The alkyl bromide reactions were experimentally unique in that we were able to deduce kinetics of the Cl atom reaction with bromoethane, n-bromopropane, and 1,2-dibromoethane by monitoring the appearance of the Br product by LFP-RF. The Br is formed via elimination that occurs essentially instantaneously following β-H abstraction by the Cl atom. All three of the bromoalkanes investigated are emitted into the atmosphere primarily from anthropogenic sources and all three have been identified by the World Meteorological Organization (WMO) as very short-lived (lifetime less than 6 months) source gases with significant ozone depletion potentials (ODPs). Additionally, the bromoalkanes mentioned above have been of interest as model compounds for larger partially halogenated organics found in the atmosphere, and they have been considered as potential replacement compounds for chlorofluorocarbons (CFCs) that have been banned as a result of the Montreal Protocol. Brominated very short-lived compounds are thought to contribute 20-25% of total stratospheric bromine. Thus, there is considerable interest in understanding the atmospheric chemistry of even the most short-lived organic bromine compounds. Temporal profiles of Br atoms provided important kinetic and mechanistic insight for the reactions over a wide range of temperature and pressure. Temperature-dependent rate coefficients are determined for the alkyl bromides of interest for the first time, and the potential importance of the Cl reaction as an…
Advisors/Committee Members: Paul Wine (Committee Chair), Athanasios Nenes (Committee Member), Greg Huey (Committee Member), Rodney Weber (Committee Member), Thomas Orlando (Committee Member).
Subjects/Keywords: Bromine atom reactions; Chlorine atom reactions; Halogen atoms; Gas phase reactions; Free radical reactions; Free radicals (Chemistry); Chemical reactions; Thermochemistry; Atmosphere; Atmosphere Laser observations
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APA (6th Edition):
Laine, P. L. (2011). Laser flash photolysis studies of halogen atom reactions of atmospheric interest. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/42817
Chicago Manual of Style (16th Edition):
Laine, Patrick L. “Laser flash photolysis studies of halogen atom reactions of atmospheric interest.” 2011. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/42817.
MLA Handbook (7th Edition):
Laine, Patrick L. “Laser flash photolysis studies of halogen atom reactions of atmospheric interest.” 2011. Web. 25 Jan 2021.
Vancouver:
Laine PL. Laser flash photolysis studies of halogen atom reactions of atmospheric interest. [Internet] [Doctoral dissertation]. Georgia Tech; 2011. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/42817.
Council of Science Editors:
Laine PL. Laser flash photolysis studies of halogen atom reactions of atmospheric interest. [Doctoral Dissertation]. Georgia Tech; 2011. Available from: http://hdl.handle.net/1853/42817
2.
Asa-Awuku, Akua Asabea.
Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor.
Degree: PhD, Chemical Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/22658
► Aerosols have significant impacts on earth's climate and hydrological cycle. They can directly reflect the amount of incoming solar radiation into space; by acting as…
(more)
▼ Aerosols have significant impacts on earth's climate and hydrological cycle. They can directly reflect the amount of incoming solar radiation into space; by acting as cloud condensation nuclei (CCN), they can indirectly impact climate by affecting cloud albedo. Our current assessment of the interactions of aerosols and clouds is uncertain and parameters used to estimate cloud droplet formation in global climate models are not well constrained. Organic aerosols attribute much of the uncertainty in these estimates and are known to affect the ability of aerosol to form cloud droplets (CCN Activity) by i) providing solute, thus reducing the equilibrium water vapor pressure of the droplet and ii) acting as surfactants capable of depressing surface tension, and potentially, growth kinetics. My thesis dissertation investigates various organic aerosol species (e.g., marine, urban, biomass burning, Humic-like Substances). An emphasis is placed on the water soluble components and secondary organic aerosols (SOA). In addition the sampled organic aerosols are acquired via different media; directly from in-situ ambient studies (TEXAQS 2006) environmental chamber experiments, regenerated from filters, and cloud water samples. Novel experimental methods and analyses to determine surface tension, molar volumes, and droplet growth rates are presented from nominal volumes of sample. These key parameters for cloud droplet formation incorporated into climate models will constrain aerosol-cloud interactions and provide a more accurate assessment for climate prediction.
Advisors/Committee Members: Athanasios Nenes (Committee Chair), Amyn Teja (Committee Member), Carson Merideth (Committee Member), Michael Bergin (Committee Member), Rodney Weber (Committee Member).
Subjects/Keywords: Kohler theory analysis; Cloud condensation nuclei; Water-soluble organic compounds; CCN closure; Aerosols; Cloud physics; Organic compounds
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APA (6th Edition):
Asa-Awuku, A. A. (2008). Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/22658
Chicago Manual of Style (16th Edition):
Asa-Awuku, Akua Asabea. “Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor.” 2008. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/22658.
MLA Handbook (7th Edition):
Asa-Awuku, Akua Asabea. “Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor.” 2008. Web. 25 Jan 2021.
Vancouver:
Asa-Awuku AA. Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/22658.
Council of Science Editors:
Asa-Awuku AA. Characterizing water-soluble organic aerosol and their effects on cloud droplet formation: Interactions of carbonaceous matter with water vapor. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/22658
3.
Barahona, Donifan.
On the representation of aerosol-cloud interactions in atmospheric models.
Degree: PhD, Chemical Engineering, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/41169
► Anthropogenic atmospheric aerosols (suspended particulate matter) can modify the radiative balance (and climate) of the Earth by altering the properties and global distribution of clouds.…
(more)
▼ Anthropogenic atmospheric aerosols (suspended particulate matter) can modify the radiative balance (and climate) of the Earth by altering the properties and global distribution of clouds. Current climate models however cannot adequately account for many important aspects of these aerosol-cloud interactions, ultimately leading to a large uncertainty in the estimation of the magnitude of the effect of aerosols on climate. This thesis focuses on the development of physically-based descriptions of aerosol-cloud processes in climate models that help to address some of such predictive uncertainty. It includes the formulation of a new analytical parameterization for the formation of ice clouds, and the inclusion of the effects of mixing and kinetic limitations in existing liquid cloud parameterizations. The parameterizations are analytical solutions to the cloud ice and water particle nucleation problem, developed within a framework that considers the mass and energy balances associated with the freezing and droplet activation of aerosol particles. The new frameworks explicitly account for the impact of cloud formation dynamics, the aerosol size and composition, and the dominant freezing mechanism (homogeneous vs. heterogeneous) on the ice crystal and droplet concentration and size distribution. Application of the new parameterizations is demonstrated in the NASA Global Modeling Initiative atmospheric and chemical and transport model to study the effect of aerosol emissions on the global distribution of ice crystal concentration, and, the effect of entrainment during cloud droplet activation on the global cloud radiative properties. The ice cloud formation framework is also used within a parcel ensemble model to understand the microphysical structure of cirrus clouds at very low temperature. The frameworks developed in this work provide an efficient, yet rigorous, representation of cloud formation processes from precursor aerosol. They are suitable for the study of the effect of anthropogenic aerosol emissions on cloud formation, and can contribute to the improvement of the predictive ability of atmospheric models and to the understanding of the impact of human activities on climate.
Advisors/Committee Members: Athanasios Nenes (Committee Chair), Amyn S. Teja (Committee Member), Irina Sokolik (Committee Member), Judith A. Curry (Committee Member), Martha A. Grover (Committee Member).
Subjects/Keywords: Giant CCN; Entrainment; Cloud-climate interactions; Clouds; Cloud formation; Parameterization; Aerosol indirect effect; Ice; Atmospheric aerosols; Cloud physics; Clouds Dynamics
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APA (6th Edition):
Barahona, D. (2010). On the representation of aerosol-cloud interactions in atmospheric models. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/41169
Chicago Manual of Style (16th Edition):
Barahona, Donifan. “On the representation of aerosol-cloud interactions in atmospheric models.” 2010. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/41169.
MLA Handbook (7th Edition):
Barahona, Donifan. “On the representation of aerosol-cloud interactions in atmospheric models.” 2010. Web. 25 Jan 2021.
Vancouver:
Barahona D. On the representation of aerosol-cloud interactions in atmospheric models. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/41169.
Council of Science Editors:
Barahona D. On the representation of aerosol-cloud interactions in atmospheric models. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/41169
4.
Hsieh, Wei-Chun.
Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies.
Degree: PhD, Earth and Atmospheric Sciences, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/29619
► The indirect effect of aerosols expresses how changes in aerosols would influence clouds and cause impacts on Earth's climate and hydrological cycle. The current assessment…
(more)
▼ The indirect effect of aerosols expresses how changes in aerosols would influence clouds and cause impacts on Earth's climate and hydrological cycle. The current assessment of the interactions between aerosols and clouds is uncertain and parameterizations used to represent cloud processes are not well constrained. This thesis first evaluates a cloud activation parameterization by investigating cloud droplet number concentration closure for stratocumulus clouds sampled during the 2005 MArine Stratus Experiment (MASE). Further analysis of the droplet size distribution characteristics using the extended parameterization is performed by comparing the predicted droplet spectra with the observed ones. The effect of dynamical variability on the droplet size distribution evolution is also investigated by considering a probability density function for updraft velocity. The cumulus and stratocumulus cloud datasets from in-situ field measurements of NASA's Cirrus Regional Study of Tropical Anvils and Cirrus Layers - Florida Area Cirrus Experiment (CRYSTAL-FACE) and Coastal STRatocumulus Imposed Perturbation Experiment (CSTRIPE) campaigns are used for this task. Using the same datasets, the autoconversion rate is calculated based on direct integration of kinematic collection equation (KCE). Six autoconversion parameterizations are evaluated and the effect of turbulence on magnifying collection process is also considered. Finally, a general circulation model (GCM) is used for studying the effect of different autoconversion parameterizations on indirect forcing estimates. The autoconversion rate given by direct KCE integration is also included by implementing a look-up table for collection kernels. Although these studies add more variability to the current estimate of aerosol indirect forcing, they also provide direction towards a more accurate assessment for climate prediction.
Advisors/Committee Members: Athanasios Nenes (Committee Chair), Andrew G. Stack (Committee Member), Irina N. Sokolik (Committee Member), Judith A. Curry (Committee Member), Mike Bergin (Committee Member), Rodney J. Weber (Committee Member).
Subjects/Keywords: Autoconversion; Aerosol indirect effect; Cloud physics; Aerosols; Hydrologic cycle; Drops
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APA (6th Edition):
Hsieh, W. (2009). Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/29619
Chicago Manual of Style (16th Edition):
Hsieh, Wei-Chun. “Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies.” 2009. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/29619.
MLA Handbook (7th Edition):
Hsieh, Wei-Chun. “Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies.” 2009. Web. 25 Jan 2021.
Vancouver:
Hsieh W. Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/29619.
Council of Science Editors:
Hsieh W. Representing droplet size distribution and
cloud processes in aerosol-cloud-climate
interaction studies. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/29619
5.
Nwanosike, Quinta M.
Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies.
Degree: PhD, Chemical Engineering, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/31736
► Crystallization of proteins in the human body can lead to the development of diseases such as sickle cell anemia and cataract. Understanding protein crystallization can…
(more)
▼ Crystallization of proteins in the human body can lead to the development of diseases such as sickle cell anemia and cataract. Understanding protein crystallization can give insight into such diseases. Furthermore, protein crystallization is necessary for protein structure resolution. This is important since resolution of protein structure is the first step towards establishing structure/function relations, and possibly towards performing specific structural modifications that may change the function in desirable directions. Another important application of protein crystallization is in downstream processing in the pharmaceutical industry where it is used for separation and as a final purification step. The present study increases knowledge of interactions between protein molecules during crystallization and hence the crystallization process.
Crystallization of proteins in the human body can lead to the development of diseases such as sickle cell anemia and cataract. Understanding the processes involved in protein crystallization can help us gain a better understanding of such diseases. Crystallization of human gamma D-crystallin (HGD) and apoferritin, two proteins found in the lens, was studied in relation to cataract formation. Crystallization of both proteins was studied in the presence of divalent cations which are found at elevated concentrations in cataractous lenses. Results indicate that the divalent cations studied enhance crystallization of these proteins.
A thermodynamic property, the osmotic second virial coefficient, was measured in protein solutions and its value was correlated with the occurrence of crystallization. It was found that the second virial coefficient successfully predicted crystallization of both proteins. A new method was developed for indirect measurement of the second virial coefficient using dynamic light scattering. This new method is more robust and efficient than the traditional static light scattering method.
Finally the ability of solubilizers to prevent crystallization in HGD solutions was studied. A commercial solubilizer, NDSB-201, was found to increase the energy barrier to nucleation. Although this did not prevent crystallization, it resulted in fewer and smaller crystals being obtained. The naturally occurring alpha A-crystallin was a superior solubilizer to NDSB-201, as it suppressed aggregation and prevented crystallization of HGD under conditions for which NDSB-201 did not. The findings in the present study provide insight into the processes by which protein crystallization occurs and hence into diseases associated with protein crystallization.
The findings in the present study provide insight into the processes by which protein crystallization occurs. Using the second virial coefficient to assess whether a protein will crystallize out of solution, approaches for retardation and prevention of protein crystallization, and implications for future research, are discussed.
Advisors/Committee Members: Ronald Rousseau (Committee Chair), Athanassios Sambanis (Committee Co-Chair), Amyn Teja (Committee Member), Athanasios Nenes (Committee Member), Ingeborg Schmidt-Krey (Committee Member).
Subjects/Keywords: Light scattering; Cataract; Second virial coefficient; Apoferritin; Protein crystallization; Gamma D-crystallin; Light Scattering; Proteins; Cations; Crystal growth
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APA (6th Edition):
Nwanosike, Q. M. (2009). Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/31736
Chicago Manual of Style (16th Edition):
Nwanosike, Quinta M. “Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies.” 2009. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/31736.
MLA Handbook (7th Edition):
Nwanosike, Quinta M. “Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies.” 2009. Web. 25 Jan 2021.
Vancouver:
Nwanosike QM. Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/31736.
Council of Science Editors:
Nwanosike QM. Effect of divalent cations and solubilizers in apoferritin and gamma D-crystallin solutions: nucleation, crystallization and light scattering studies. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/31736
Georgia Tech
6.
Asa-Awuku, Akua Asabea.
The effect of solute dissolution kinetics on cloud droplet formation.
Degree: MS, Chemical Engineering, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/10456
► This study focuses on the importance of solute dissolution kinetics for cloud droplet formation. To comprehensively account for the kinetics, a numerical model of the…
(more)
▼ This study focuses on the importance of solute dissolution kinetics for cloud droplet formation. To comprehensively account for the kinetics, a numerical model of the process was developed. Simulations of cloud droplet growth were performed for solute diffusivity, droplet growth rates, dry particle and droplet diameters relevant for ambient conditions. Simulations suggest that high ambient supersaturations and a decrease in solute diffusivity are major contributors to significant decreases in effective solute surface concentrations. The numerical simulations were incorporated into Khler theory to assess the impact of dissolution kinetics on the droplet equilibrium vapor pressure. For CCN composed of partially soluble material, a significant increase was found in the equilibrium supersaturation of CCN.
Advisors/Committee Members: Dr. Athanasios Nenes (Committee Chair), Dr. Amyn Teja (Committee Member), Dr. Rodney Weber (Committee Member).
Subjects/Keywords: Cloud droplet formation; Activation; Dissolution kinetics; Aerosols; Clouds; Atmosphere, Upper Mathematical models; Drops; Climatology Mathematical models
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APA (6th Edition):
Asa-Awuku, A. A. (2006). The effect of solute dissolution kinetics on cloud droplet formation. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/10456
Chicago Manual of Style (16th Edition):
Asa-Awuku, Akua Asabea. “The effect of solute dissolution kinetics on cloud droplet formation.” 2006. Masters Thesis, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/10456.
MLA Handbook (7th Edition):
Asa-Awuku, Akua Asabea. “The effect of solute dissolution kinetics on cloud droplet formation.” 2006. Web. 25 Jan 2021.
Vancouver:
Asa-Awuku AA. The effect of solute dissolution kinetics on cloud droplet formation. [Internet] [Masters thesis]. Georgia Tech; 2006. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/10456.
Council of Science Editors:
Asa-Awuku AA. The effect of solute dissolution kinetics on cloud droplet formation. [Masters Thesis]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/10456
Georgia Tech
7.
Williams, Robyn D.
Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform.
Degree: MS, Chemical Engineering, 2005, Georgia Tech
URL: http://hdl.handle.net/1853/7252
► Cirrus clouds cover between 20% - 50% of the globe and are an essential component in the climate. The improved understanding of ice cloud microphysical…
(more)
▼ Cirrus clouds cover between 20% - 50% of the globe and are an essential
component in the climate. The improved understanding of ice cloud
microphysical properties is contingent on acquiring and analyzing in-situ and
remote sensing data from cirrus clouds. In ??u observations of microphysical
properties of ice and mixed-phase clouds using the mini-Video Ice Particle Sizer
(mini-VIPS) aboard robotic unmanned aerial vehicles (UAVs) provide a promising
and powerful platform for obtaining valuable data in a cost-effective, safe, and
long-term manner.
The purpose of this study is to better understand cirrus microphysical
properties by analyzing the effectiveness of the mini-VIPS/UAV in-situ platform.
The specific goals include:
(1) To validate the mini-VIPS performance by comparing the mini-VIPS data
retrieved during an Artic UAV mission with data retrieved from the millimeterwavelength
cloud radar (MMCR) at the Barrow ARM/CART site.
(2) To analyze mini-VIPS data to survey the properties of high latitude mixedphase
clouds
The intercomparison between in-situ and remote sensing measurements
was carried out by comparing reflectivity values calculated from in-situ
measurements with observations from the MMCR facility. Good agreement
between observations and measurements is obtained during the time frame
where the sampled volume was saturated with respect to ice. We also have
1 2
shown that the degree of closure between calculated and observed reflectivity
strongly correlates with the assumption of ice crystal geometry observed in the
mini-VIPS images. The good correlation increases the confidence in mini-VIPS
and MMCR measurements. Finally, the size distribution and ice crystal geometry
obtained from the data analysis is consistent with published literature for similar
conditions of temperature and ice supersaturation.
Advisors/Committee Members: Dr. Athanasios Nenes (Committee Chair), Dr. Amyn Teja (Committee Member), Dr. Judith Curry (Committee Member).
Subjects/Keywords: MMCR; Climate; Cloud; Mini-VIPS; Microphysics; Ice clouds Measurement; Drone aircraft; Clouds Remote sensing; Cloud physics Analysis
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APA ·
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APA (6th Edition):
Williams, R. D. (2005). Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform. (Masters Thesis). Georgia Tech. Retrieved from http://hdl.handle.net/1853/7252
Chicago Manual of Style (16th Edition):
Williams, Robyn D. “Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform.” 2005. Masters Thesis, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/7252.
MLA Handbook (7th Edition):
Williams, Robyn D. “Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform.” 2005. Web. 25 Jan 2021.
Vancouver:
Williams RD. Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform. [Internet] [Masters thesis]. Georgia Tech; 2005. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/7252.
Council of Science Editors:
Williams RD. Studies of Mixed-Phase Cloud Microphysics Using An In-Situ Unmanned Aerial Vehicle (UAV) Platform. [Masters Thesis]. Georgia Tech; 2005. Available from: http://hdl.handle.net/1853/7252
Georgia Tech
8.
Fountoukis, Christos.
Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments.
Degree: PhD, Chemical Engineering, 2007, Georgia Tech
URL: http://hdl.handle.net/1853/16242
► The current dissertation is motivated by the need for an improved understanding of aerosol water interactions both in subsaturated and supersaturated atmospheric conditions with a…
(more)
▼ The current dissertation is motivated by the need for an improved understanding of aerosol water interactions both in subsaturated and supersaturated atmospheric conditions with a strong emphasis on air pollution and climate change modeling. A cloud droplet formation parameterization was developed to i) predict droplet formation from a lognormal representation of aerosol size distribution and composition, and, ii) include a size-dependant mass transfer coefficient for the growth of water droplets which explicitly accounts for the impact of organics on droplet growth kinetics. The parameterization unravels most of the physics of droplet formation and is in remarkable agreement with detailed numerical parcel model simulations, even for low values of the accommodation
coefficient. The parameterization offers a much needed rigorous and computationally inexpensive framework for directly linking complex chemical effects on aerosol activation in global climate models.
The new aerosol activation parameterization was also tested against observations from highly polluted clouds (within the vicinity of power plant plumes). Remarkable closure was achieved (much less than the 20% measurement uncertainty). The error in predicted cloud droplet concentration was mostly sensitive to updraft velocity. Optimal closure is obtained if the water vapor uptake coefficient is equal to 0.06. These findings can serve as much needed constraints in modeling of aerosol-cloud interactions in the North America.
Aerosol water interactions in ambient relative humidities less than 100% were studied
using a thermodynamic equilibrium model for inorganic aerosol and a three dimensional air quality model. We developed a new thermodynamic equilibrium model, ISORROPIA-II, which predicts the partitioning of semi-volatiles and the phase state of K+/Ca2+/Mg2+/NH4+/Na+/SO42-/NO3-/Cl-/H2O aerosols. A comprehensive evaluation of its performance was conducted against the thermodynamic module SCAPE2 over a wide range of atmospherically relevant conditions. Based on its computational rigor and performance, ISORROPIA-II appears to be a highly attractive alternative for use in large scale air quality and atmospheric transport models.
The new equilibrium model was also used to thermodynamically characterize aerosols measured at a highly polluted area. In the ammonia-rich environment of Mexico City, nitrate and chloride primarily partition in the aerosol phase with a 20-min equilibrium timescale; PM2.5 is insensitive to changes in ammonia but is to acidic semivolatile species. When RH is below 50%, predictions improve substantially if the aerosol follows a deliquescent behavior.
The impact of including crustal species (Ca2+, K+, M2+) in equilibrium calculations within
a three dimensional air quality model was also studied. A significant change in aerosol
water (-19.8%) and ammonium (-27.5%) concentrations was predicted when crustals are
explicitly included in the calculations even though they contributed, on average, only a
few percent of the total PM2.5…
Advisors/Committee Members: Athanasios Nenes (Committee Chair), Amyn Teja (Committee Member), Joseph Schork (Committee Member), Rodney Weber (Committee Member), Rong Fu (Committee Member).
Subjects/Keywords: Aerosol phase state; Cloud droplet; Aerosol equilibrium; Air quality modeling; Global climate model; Aerosol activation
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APA (6th Edition):
Fountoukis, C. (2007). Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/16242
Chicago Manual of Style (16th Edition):
Fountoukis, Christos. “Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments.” 2007. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/16242.
MLA Handbook (7th Edition):
Fountoukis, Christos. “Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments.” 2007. Web. 25 Jan 2021.
Vancouver:
Fountoukis C. Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments. [Internet] [Doctoral dissertation]. Georgia Tech; 2007. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/16242.
Council of Science Editors:
Fountoukis C. Modeling Aerosol - Water Interactions in Subsaturated and Supersaturated Environments. [Doctoral Dissertation]. Georgia Tech; 2007. Available from: http://hdl.handle.net/1853/16242
Georgia Tech
9.
Yoshida, Yasuko.
Global sources and distribution of atmospheric methyl chloride.
Degree: PhD, Earth and Atmospheric Sciences, 2006, Georgia Tech
URL: http://hdl.handle.net/1853/11537
► Global simulations of atmospheric methyl chloride (CH3Cl) are conducted using the GEOS-Chem model in order to understand better its sources and sinks. Though CH3Cl is…
(more)
▼ Global simulations of atmospheric methyl chloride (CH3Cl) are conducted using the GEOS-Chem model in order to understand better its sources and sinks. Though CH3Cl is one of the most abundant organic chlorine species in the stratosphere, not much is known about its sources and the budget remains unbalanced. In addition to the known sources (1.5 Tg yr-1) from ocean, biomass burning, incineration/industry, salt marshes, and wetlands, a hypothetical aseasonal biogenic source of 2.9 Tg yr-1 is added in order to match needed emissions. Observations from 7 surface sites and 8 aircraft field experiments are used to evaluate the model simulations. The model results with a priori emissions and sinks reproduce CH3Cl observations at northern mid and high latitudes reasonably well. However, the seasonal variation of CH3Cl at southern mid and high latitudes is severely overestimated. Simulated vertical profiles show disagreements in the vicinities of major sources, principally reflecting the uncertainties in the estimated distributions of our added pseudo-biogenic and the biomass burning sources. Inverse modeling is applied to obtain optimal source distributions of CH3Cl on the basis of surface and aircraft observations and model results. We resolve the seasonal dependence of the biogenic and biomass burning sources for each hemisphere. The aircraft in situ measurements are found to provide better constraints on the emission sources than surface measurements. The a posteriori emissions result in better agreement with the observations particularly at southern high latitudes. The a posteriori biogenic and biomass burning source decrease by 13 and 11% to 2500 and 545 Gg yr-1, respectively, while the a posteriori net ocean source increases by about a factor of 2 to 761 Gg yr-1. The decrease in biomass burning emissions is largely due to the reduction in the emissions in seasons other than spring in the northern hemisphere. The inversion results indicate that the biogenic source has a clear winter minimum in both hemispheres, likely reflecting the decrease of biogenic activity during that season.
Advisors/Committee Members: Yuhang Wang (Committee Chair), Armistead Russell (Committee Member), Athanasios Nenes (Committee Member), David Tan (Committee Member), Robert Dickinson (Committee Member).
Subjects/Keywords: Global modeling; Sources and sinks; Bayesian; Inverse modeling; Methyl chloride; Sinks (Atmospheric chemistry); Atmospheric chemistry Observations; Atmospheric chlorine compounds Mathematical models
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APA (6th Edition):
Yoshida, Y. (2006). Global sources and distribution of atmospheric methyl chloride. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/11537
Chicago Manual of Style (16th Edition):
Yoshida, Yasuko. “Global sources and distribution of atmospheric methyl chloride.” 2006. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/11537.
MLA Handbook (7th Edition):
Yoshida, Yasuko. “Global sources and distribution of atmospheric methyl chloride.” 2006. Web. 25 Jan 2021.
Vancouver:
Yoshida Y. Global sources and distribution of atmospheric methyl chloride. [Internet] [Doctoral dissertation]. Georgia Tech; 2006. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/11537.
Council of Science Editors:
Yoshida Y. Global sources and distribution of atmospheric methyl chloride. [Doctoral Dissertation]. Georgia Tech; 2006. Available from: http://hdl.handle.net/1853/11537
Georgia Tech
10.
Zhao, Chun.
Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia.
Degree: PhD, Earth and Atmospheric Sciences, 2009, Georgia Tech
URL: http://hdl.handle.net/1853/28114
► Distributions of air pollutants and their precursors in the troposphere are driven largely by meteorological conditions (e.g., wind, cloud convection, lightning, and precipitation) and emissions…
(more)
▼ Distributions of air pollutants and their precursors in the troposphere are driven largely by meteorological conditions (e.g., wind, cloud convection, lightning, and precipitation) and emissions such as those of NOx from anthropogenic sources (e.g., fossil fuel combustion) and natural sources (e.g., soils and lightning). As the most polluted regions in the world, North America and East Asia significantly contribute to climate change on both regional and global scales. Therefore, it deserves to investigate the vertical and horizontal distributions of the air pollutants in the troposphere over these two regions to better quantify the interaction between air pollution and climate change, which remains until now largely uninvestigated. Here, a Regional chEmical trAnsport Model (REAM) was developed and applied to examine the uncertainties in modeling the effect of convective transport and lightning NOx production on upper tropospheric chemical tracer distributions over North America, and to identify the features of air pollutions over East Asia.
Advisors/Committee Members: Yuhang Wang (Committee Chair), Armistead Russell (Committee Member), Athanasios Nenes (Committee Member), Greg Huey (Committee Member), Judith Curry (Committee Member).
Subjects/Keywords: Air pollution; Lightning; Convection; Tropospheric chemistry; Air Pollution; Mathematical models
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APA (6th Edition):
Zhao, C. (2009). Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/28114
Chicago Manual of Style (16th Edition):
Zhao, Chun. “Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia.” 2009. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/28114.
MLA Handbook (7th Edition):
Zhao, Chun. “Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia.” 2009. Web. 25 Jan 2021.
Vancouver:
Zhao C. Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia. [Internet] [Doctoral dissertation]. Georgia Tech; 2009. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/28114.
Council of Science Editors:
Zhao C. Impact of convection and lightning on the tropospheric chemistry composition over North America and air quality studies over East Asia. [Doctoral Dissertation]. Georgia Tech; 2009. Available from: http://hdl.handle.net/1853/28114
Georgia Tech
11.
Liao, Kuo-Jen.
Sensitivity and uncertainty analyses of impacts of climate change on regional air quality.
Degree: PhD, Civil and Environmental Engineering, 2008, Georgia Tech
URL: http://hdl.handle.net/1853/24822
► Climate change is forecast to affect ambient temperatures, precipitation frequency and stagnation conditions, all of which impact regional air quality. An issue of primary importance…
(more)
▼ Climate change is forecast to affect ambient temperatures, precipitation frequency and stagnation conditions, all of which impact regional air quality. An issue of primary importance for policy-makers is how well currently planned control strategies for improving air quality that are based on the current climate will work under future global climate change scenarios. The US EPA s Regional Air Quality Modeling System, CMAQ, with DDM-3D are used to investigate sensitivities of ozone and PM2.5 to emissions for current and future scenarios. Sensitivities are predicted to change slightly in response to climate change. In many cases, mass per ton sensitivities to NOx and SO2 controls are predicted to be greater in the future due to both the lower emissions as well as climate, suggesting that current control strategies based on reducing such emissions will continue to be effective in decreasing ozone and PM2.5 levels. Impacts of climate uncertainties on regional air quality predictions are investigated using multiple climate futures in order to evaluate the robustness of currently planned emission controls under impacts of climate change. The results show that planned controls for decreasing regional ozone and PM2.5 will continue to be effective in the future under the extreme climate scenarios. However, the impact of climate uncertainties may be substantial in some urban areas and should be included in assessing future regional air quality and emission control requirements. Furthermore, daily cross-responses of ozone and PM2.5 to emissions are investigated for current and future scenarios. Planned controls of NOx emissions are predicted to lead to more positive responses in reducing urban ozone and PM2.5 levels in the future. Based on present emission control technologies, cost optimized emission reductions for offsetting impacts of climate change on regional peak fourth-highest daily maximum 8-hr average ozone and yearly average PM2.5 are predicted to range from 27 million to 5.9 billion (1999) per year in 2050s for the cities examined in this study.
Advisors/Committee Members: Armistead G. Russell (Committee Chair), Athanasios Nenes (Committee Member), M. Talat Odman (Committee Member), Michael Bergin (Committee Member), Yuhang Wang (Committee Member).
Subjects/Keywords: Sensitivity; Uncertainty; Climate change; Air quality; Climatic changes; Air quality management
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APA (6th Edition):
Liao, K. (2008). Sensitivity and uncertainty analyses of impacts of climate change on regional air quality. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/24822
Chicago Manual of Style (16th Edition):
Liao, Kuo-Jen. “Sensitivity and uncertainty analyses of impacts of climate change on regional air quality.” 2008. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/24822.
MLA Handbook (7th Edition):
Liao, Kuo-Jen. “Sensitivity and uncertainty analyses of impacts of climate change on regional air quality.” 2008. Web. 25 Jan 2021.
Vancouver:
Liao K. Sensitivity and uncertainty analyses of impacts of climate change on regional air quality. [Internet] [Doctoral dissertation]. Georgia Tech; 2008. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/24822.
Council of Science Editors:
Liao K. Sensitivity and uncertainty analyses of impacts of climate change on regional air quality. [Doctoral Dissertation]. Georgia Tech; 2008. Available from: http://hdl.handle.net/1853/24822
Georgia Tech
12.
Kaisare, Niket S.
Modeling, Analysis and Control of Nonlinear Switching Systems.
Degree: PhD, Chemical Engineering, 2004, Georgia Tech
URL: http://hdl.handle.net/1853/6976
► The first part of this two-part thesis examines the reverse-flow operation of auto-thermal methane reforming in a microreactor. A theoretical study is undertaken to explain…
(more)
▼ The first part of this two-part thesis examines the reverse-flow operation of auto-thermal methane reforming in a microreactor. A theoretical study is undertaken to explain the physical origins of the experimentally observed improvements in the performance of the reverse-flow operation compared to the unidirectional operation. First, a scaling analysis is presented to understand the effect of various time scales existing within the microreactor, and to obtain guidelines for the optimal reverse-flow operation. Then, the effect of kinetic parameters, transport properties, reactor design and operating conditions on the reactor operation is parametrically studied through numerical simulations. The reverse-flow operation is shown to be more robust than the unidirectional operation with respect to both optimal operating conditions as well as variations in hydrogen throughput requirements. A rational scheme for improved catalyst placement in the microreactor, which exploits the spatial temperature profiles in the reactor, is also presented. Finally, a design modification of the microreactor called "opposed-flow" reactor, which retains the performance benefits of the reverse-flow operation without requiring the input / output port switching, is suggested.
In the second part of this thesis, a novel simulation-based Approximate Dynamic Programming (ADP) framework is presented for optimal control of switching between multiple metabolic states in a microbial bioreactor. The cybernetic modeling framework is used to capture these cellular metabolic switches. Model Predictive Control, one of the most popular advanced control methods, is able to drive the reactor to the desired steady state. However, the nonlinearity and switching nature of the system cause computational and performance problems with MPC. The proposed ADP has an advantage over MPC, as the closed-loop optimal policy is computed offline in the form of so-called value or cost-to-go function. Through the use of an approximation of the value function, the infinite horizon problem is converted into an equivalent single-stage problem, which can be solved online. Various issues in implementation of ADP are also addressed.
Advisors/Committee Members: Jay H. Lee (Committee Chair), Andrei G. Fedorov (Committee Member), Athanasios Nenes (Committee Member), Martha Gallivan (Committee Member), Matthew Realff (Committee Member).
Subjects/Keywords: Reinforcement learning; Partial oxidation; Microreactor; Reverse flow; Dynamic programming
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APA (6th Edition):
Kaisare, N. S. (2004). Modeling, Analysis and Control of Nonlinear Switching Systems. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/6976
Chicago Manual of Style (16th Edition):
Kaisare, Niket S. “Modeling, Analysis and Control of Nonlinear Switching Systems.” 2004. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/6976.
MLA Handbook (7th Edition):
Kaisare, Niket S. “Modeling, Analysis and Control of Nonlinear Switching Systems.” 2004. Web. 25 Jan 2021.
Vancouver:
Kaisare NS. Modeling, Analysis and Control of Nonlinear Switching Systems. [Internet] [Doctoral dissertation]. Georgia Tech; 2004. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/6976.
Council of Science Editors:
Kaisare NS. Modeling, Analysis and Control of Nonlinear Switching Systems. [Doctoral Dissertation]. Georgia Tech; 2004. Available from: http://hdl.handle.net/1853/6976
Georgia Tech
13.
Hecobian, Arsineh N.
Investigating water soluble organic aerosols: sources and evolution.
Degree: PhD, Earth and Atmospheric Sciences, 2010, Georgia Tech
URL: http://hdl.handle.net/1853/33819
► An existing method for the measurement of atmospheric gaseous species was modified to collect data on aerosol concentrations. Data from biomass burning events in different…
(more)
▼ An existing method for the measurement of atmospheric gaseous species was modified to collect data on aerosol concentrations. Data from biomass burning events in different regions (Canada, the Arctic and California) were collected during April to July, 2008 and the concentrations and evolution of secondary organic aerosols were discussed. And finally, data on the light absorbing properties of water soluble organic aerosols were collected in Atlanta, GA and compared with filter data for the same properties. The results presented in this thesis showed that a negative ion chemical ionization mass spectrometer (CIMS), can be modified by the addition of a thermally denuded inlet to measure aerosol phase sulfuric acid. This system can also be used to measure other aerosol phase organic acids. In the biomass burning plumes studied in the second part, no clear indication of formation of secondary aerosol or gaseous species was observed, except for peroxyacetyl nitrate (PAN). Filter data collected from FRM sites in the Southeastern U.S. showed that biomass burning is the most dominant source of water soluble light absorbing carbonaceous aerosol in this region. The data from a study in Atlanta, GA showed that the online PILS-LWCC-WSOC system might be used for measurements of light absorbing properties of aerosols and WSOC.
Advisors/Committee Members: Dr. Rodney J. Weber (Committee Chair), Dr. Athanasios Nenes (Committee Member), Dr. L. Gregory Huey (Committee Member), Dr. Michael Bergin (Committee Member), Dr. Paul H. Wine (Committee Member).
Subjects/Keywords: CIMS; Biomass burning; Brown carbon; PILS; Organic aerosols; ARCTAS; Aerosols; Organic compounds
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APA ·
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MLA ·
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CSE |
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Manager
APA (6th Edition):
Hecobian, A. N. (2010). Investigating water soluble organic aerosols: sources and evolution. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/33819
Chicago Manual of Style (16th Edition):
Hecobian, Arsineh N. “Investigating water soluble organic aerosols: sources and evolution.” 2010. Doctoral Dissertation, Georgia Tech. Accessed January 25, 2021.
http://hdl.handle.net/1853/33819.
MLA Handbook (7th Edition):
Hecobian, Arsineh N. “Investigating water soluble organic aerosols: sources and evolution.” 2010. Web. 25 Jan 2021.
Vancouver:
Hecobian AN. Investigating water soluble organic aerosols: sources and evolution. [Internet] [Doctoral dissertation]. Georgia Tech; 2010. [cited 2021 Jan 25].
Available from: http://hdl.handle.net/1853/33819.
Council of Science Editors:
Hecobian AN. Investigating water soluble organic aerosols: sources and evolution. [Doctoral Dissertation]. Georgia Tech; 2010. Available from: http://hdl.handle.net/1853/33819
. 
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